Bistella 500, a 500cc 2 Stroke, 2 Row, Supercharged, 10 Cylinder Radial Engine Custom Motorcycle by Marek Foltis

Let me get right to the point, this engine build/custom motorcycle by Marek Foltis is one of the most impressive homebuilt projects I’ve seen since starting The Kneeslider in 2004. It’s that good. It began when Marek challenged himself with almost impossible goals, followed by absolute personal commitment to learning and doing whatever it took to get the job done. This project is as much about Marek’s attitude as it is about the engine he designed and the finished motorcycle you see here.

So, what is the Bistella 500? The focal point is the extraordinary 500cc 2 stroke, 2 row, supercharged, 10 cylinder radial engine. Let that sink in while considering, it’s installed in a motorcycle replacing the stock single cylinder engine without modifying the frame and the finished motorcycle is road legal in the EU. This project is the epitome of thinking, “I wonder if I could … ” and then finding out.

Marek’s primary goal was to build something completely different, an engine of his own unique design, but, as most of you know, it isn’t easy because we’ve seen so many variations of size and configuration, you start to wonder, what’s left that hasn’t been done many times before? To complicate matters, CAD templates and formulas exist allowing you to plug in some numbers and after calculations are complete, you end up with a design for an inline four or V-Twin or whatever else you might choose, even if you don’t know anything about engineering, physics or material science, so Marek chose to go where there are no ready-made templates and formulas, where he would have to figure it out all on his own.

He also wanted to push the mechanical complexity of this project as far as possible, and to that point we can say, “Mission Accomplished,” and he went right to the edge, too, he says, “One step further in complexity and I would have needed magic, not science, to make the engine work.”

The next two goals were interrelated: to have as many cylinders as possible and to have a road legal motorcycle in the end. Radial engines are a very space effective way to add cylinders, but as you add cylinders the diameter of the engine increases. The motorcycle he began with was a 1953 Jawa Perak, obviously not designed for a large powerful engine, but his engine had to fit without modifying the stock frame and components because doing so would have made getting the necessary paperwork to make it road legal almost impossible. So after trying all sorts of design combinations with 8, 10 and 12 cylinders, he settled on 10 cylinders in two rows and he was able to make it fit with 1mm of clearance to spare. (In Marek’s mind, it was the obvious solution, who among the rest of us would even imagine it?)

In our communications back and forth, one thing jumped out immediately, Marek’s positive attitude. He knew going in, it was going to be hard, as any worthwhile project is, but he was confident the inevitable problems could be solved. Beyond that, he wanted to inspire others, showing how total commitment to their dream and not giving up in the face of obstacles was the secret to success. I like this guy!

The engine has one crankshaft with 2 master rods reducing engine diameter and height, but a blower is necessary to maintain the scavenging cycle, but this bike has no room for some bolt on blower so Marek came up with an ingenious solution, five tiny roots type superchargers essentially hidden inside the engine. Marek notes: “Using 5 tiny blowers is more space effective and allowed me to use high (up to 40,000) blower rpm so they can be small and still be capable of charging the engine.“ (Once again, who does this? Five tiny, gear driven, roots type blowers inside the engine! )

So far, so good, the radial engine is coming together, but a thought may have occurred to some of you, since this engine sits on top of the Jawa bottom end, how do you transmit power from a vertical crankshaft into the transmission? Well, just as you might imagine, through a bevel gear. The bottom of the radial engine is designed to fit precisely into the opening previously occupied by the single cylinder and the bevel gear is attached to the end of the radial engine’s crankshaft which mates to an internal bevel drive gear mounted on a horizontal shaft replacing the original crankshaft.

But wait, you might ask, that transmission isn’t designed for the power this radial can produce, how do you keep it from breaking? Marek thought of that:

It was significantly modified to withstand more power. These motorbikes were widely used for competitions in the 60s and Jawa made some “performance parts” back in the days so it is possible to cherry-pick those performance parts on junk “bazaars” that’s why the clutch cover differs from stock, its because the bigger clutch is under it … so I made the strongest set up possible from available Jawa parts. It was easier and more reliable than designing it myself. The funny thing is that it wasn’t cheaper than manufacturing it because these old Jawa performance parts are like relics for Jawa enthusiasts. It’s like buying original Mopar 60s-70s performance parts. I mean not Mopar expensive, but Mopar rare.

Marek tells a funny story:

There is one issue with a radial design, its master/slave rod geometry causes every cylinder to have a slightly different stroke. I solved it by adding multiple gaskets under each cylinder to make the same compression around the whole engine.
So I walked in to the spare parts store,
Me: “I want a cylinder gasket”
Salesman: “One or two?”
Me: ” SIXTY!”
Salesman stares back silently
Me: “and 25 spark plugs”
The salesman replies timidly: “That’s all I have” ” may I keep one for other customers?”

There’s so much to see here, Marek gave me some lists to help out:

Specifications:

• Base motorcycle: Jawa 18 (1953)
• Displacement: 10 x 50cc = 500ccm
• Power: now limited to 12 hp
  previously 60hp/6500 rpm (capable 120hp/10000 rpm) *see note
• Gearbox: 4speed semi-automatic
• Max speed: 110 km/h
  previously 220 km/h (137mph) (only calculated, I don’t recommend trying it) *see note
• Layout: Radial double-row two-stroke
• Aspiration: Supercharged (5x roots blower)
• Weight: 155 kg – 342 pounds

*Marek was just notified the horsepower and speed must be further limited for safety reasons, so the revised figures are stated above. Marek has changed to a smaller carburetor to restrict the engine in accordance with the new requirements

Suspension/ brakes: Friction silencers and drum brakes all stock (EU requirement can´t mess with those if I want to stay road legal)

• Engine case, crankshaft, roots blowers assembly, master connecting rods were made on CNC mill
• Cylinders, pistons, slave rods, transmission case, and clutch are used stock from vintage Jawa motorcycles
• Exhaust headers and the intake manifold are hand-made and consist of 17 hand-crafted parts. The “pipe octopus” took almost a month of cut/weld/cut/weld process. During manufacturing those tubes I got permanent inflammation in carpal tunnel area caused by angle grinder vibration. So I definitely had some fun.
• Paint job I did myself except the last layer of clear. Thick gold lines and signs are plated by pure gold.
• Pistons and combustion chambers are ceramic coated to prevent overheating

An engine this impressive must be mounted in a good looking bike. Marek did the paint and gold leaf and I like the tank top details.

Here’s where character, commitment and positive attitude come into play, some of us might call it a “gut check,” Marek blew the engine five times before getting it right, not little things either, serious damage:

1. Not enough clearance on blowers gear cover. Blower shafts touched cover and loosened the shafts screw causing it to tear the cover of the engine and busting blower bearings (oil sprayed all over workshop)
2. Second blow was because aluminum blower rotors got loose on steel drive shafts hexes caused them to rattle and then rotors touched each other resulted in inevitable jam causing gears to friction weld to shafts (prybar and hammer used during disassembly)
3. Third blow was because I was too slow during assembly and silicone hardened before I set up and assembled blowers, reducing clearance to almost zero and causing rotors to friction-weld to blowers casing after less than 1 minute run
4. Ignition stator broke and started rotating with the ignition rotor, and busted all sensors and wiring
5. I completely broke bevel gear used to connect engine to clutch. One bearing on horizontal shaft got loose it caused bevel to move a little bit that busted teeth clearance, which caused extreme teeth eroding and then slip.

More lessons learned and experiences along the way:

• First used 5 separate carbs, 1 for each blower, this assembly was impossible to tune, and I always had problems with fuel flow or fuel leak so I made intake manifold for one carb. now it works perfectly.
• First I used 10 piece CDI ignition, but it caused extreme e-mag noise and caused misfire, and digital devices could not work in 2meter radius around running bike so I removed it and now I´m using TCI (inductive) ignition. It works much better (ignition electronics is only modern technology used in this bike)
• Engine carburetors (old design) caused a fire twice, so I threw them away. (Being a living torch is not my cup of tea)
• My workshop is not heated so last winter when I was working overnight two of my toes froze black (took 8 months to heal)

Marek sums up his experience this way:

• I never gave up.
• Failure is certain but not final, unless you give up. Don’t give up.
• I committed to the pursuit of my dream with dedication.
• I worked on the project even when I didn’t feel right. The last few weeks I literally hated to be in the workshop pushing this forward.
• Now the project is finished, motorbike is running smoothly, it is EU legal (another 1 year long and boring stamp-hunting story)
• I hope that my story will make some other guys and gals day better and entertain them for a few minutes by reading or watching videos about my adventure.
• It would make all this work and suffering worthwhile if I could manage to inspire even one person to adopt responsibility for fulfilling ones dream and push against odds, never give up, don’t change direction when things get tough. For me it’s not about building a bike, it’s about conquering our inside dragons of self-doubt, fear, and false excuses … We are stronger than we think, and we have to push hard to find our strength.

If you’ve been a reader of The Kneeslider for any amount of time, you can see Marek Foltis and this project embody everything we try to find and promote, where a builder identifies a goal, a big goal, an “I wonder if it’s possible …” type of goal and then sets himself to the work ahead and doesn’t let obstacles or setbacks stand in his way. It also shows you don’t need a million dollar workshop to do fantastic work, it’s the builder that makes the difference. This project is simply spectacular and the effort and dedication necessary to carry it through is something you don’t find every day, in fact you rarely find it at all.

Marek, this is a superb job, a wonderful build and you should be extremely proud and I would expect more than a few builders will be inspired to raise the bar higher on their own projects and who knows what we may see as a result. Great work!

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UPDATE: Marek tells me he has just put up a website and I think you should bookmark it now. My guess is we’ll be seeing more interesting builds in the near future. Bistella 500

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This video is short and gives a nice look at the Bistella 500 running. Also note the double action shift and kickstart lever.:

This video is long, almost 15 minutes, the first few minutes show the bike running and some photos, then you can see the entire assembly process in high speed and it is well worth watching in its entirety.